MICROELECTRODES AS PROBES IN LOW ELECTROLYTE-SOLUTIONS - THE REDUCTION OF QUINONE IN AQUEOUS SULFURIC-ACID-SOLUTION

The steady-state voltammetric behavior of quinone in dilute aqueous so lutions of sulfuric acid has been investigated at platinum disk microe lectrodes and compared with the model presented by Oldham (J. Electroa nal. Chem., 250 (1988) 1). At high concentrations of sulfuric acid, a single voltammetric wave whose limiting current is predicted by Oldham 's model is observed. As the concentration of the sulfuric acid is low ered relative to that of the quinone, the single voltammetric wave spl its into two waves. The first wave is due to the two-electron reductio n of quinone in acidic solution and the magnitude of its limiting curr ent agrees with that predicted by Oldham's model. The second wave also results from the reduction of quinone but occurs at a more negative p otential owing to the change in pH at the electrode surface. Such a pr ocess was not considered in Oldham's model.